![]() ![]() Connection pools are one of the more obvious ways to solve that problem. NAT gateway: With a NAT gateway, you have 64k outbound SNAT ports that are usable by the resources sending traffic through it.Īvoiding the SNAT port problem means avoiding the creation of new connections repetitively to the same host and port.private endpoints: You don't have a SNAT port restriction to services secured with private endpoints.service endpoints: You don't have a SNAT port restriction to the services secured with service endpoints.connection pools: By pooling your connections, you avoid opening new network connections for calls to the same address and port.There are a few solutions that let you avoid SNAT port limitations. If your app runs out of SNAT ports, it will have intermittent outbound connectivity issues. They are then blocked until a new SNAT port becomes available, either through dynamically allocating additional SNAT ports, or through reuse of a reclaimed SNAT port. When applications or functions rapidly open a new connection, they can quickly exhaust their pre-allocated quota of the 128 ports. The Azure Network load balancer reclaims SNAT port from closed connections only after waiting for 4 minutes. Once a port has been released, the port is available for reuse as needed. The SNAT ports are used up when you have repeated calls to the same address and port combination. If your app creates connections to a mix of address and port combinations, you will not use up your SNAT ports. The SNAT port limit affects opening connections to the same address and port combination. Each instance on Azure App service is initially given a pre-allocated number of 128 SNAT ports. Azure uses source network address translation (SNAT) and Load Balancers (not exposed to customers) to communicate with public IP addresses. SNAT ports: Outbound connections in Azure describes SNAT port restrictions and how they affect outbound connections.The limit on outbound connections is associated with the size of the worker used. TCP Connections: There is a limit on the number of outbound connections that can be made.The major cause for intermittent connection issues is hitting a limit while making new outbound connections. Could not connect to external endpoints (like SQLDB, Service Fabric, other App services etc.).Slow response times on all or some of the instances in a service plan.SymptomsĪpplications and Functions hosted on Azure App service may exhibit one or more of the following symptoms: Go to the Azure Support site and select Get Support. Alternatively, file an Azure support incident. ![]() If you require more help at any point in this article, contact the Azure experts at the MSDN Azure and the Stack Overflow forums. This topic will provide more information on, and troubleshooting methodologies for, exhaustion of source network address translation (SNAT) ports. This article helps you troubleshoot intermittent connection errors and related performance issues in Azure App Service. ![]()
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